Novel non-flammable azeotrope solvent composition

ABSTRACT

TETRACHLORODIFLUOROETHANE (SYM.-, ASYM.-, AND MIXTURES THEREOF) NITROMETHANE, WATER AND ISOPROPANOL OR SECONDARY BUTANOL FORM QUATERNARY AZEOTROPIC MIXTURES WHICH ARE USEFUL AS DRY CLEANING SOLVENTS AND ARE PARTICULARLY USEFUL FOR THE REMOVAL OF HARD-TO-REMOVE STAINS FROM LEATHER.

United States Patent Office Patented Sept. 19, 1972 3,692,686 NOVELNON-FLAMMABLE AZEOTROPE SOLVENT COMPOSITION Oliver A. Barton, FlorhamPark, N.J., and Kevin P. Murphy, Orchard Park, N.Y., assignors to AlliedChemical Corporation, New York, N.Y. No Drawing. Filed Oct. 1, 1970,Ser. No. 77,388 Int. Cl. C09d 9/00; Clld 7/50; C23g /02 US. Cl. 25217110 Claims ABSTRACT OF THE DISCLOSURE Tetrachlorodifluoroethanc (sym.-,asym.-, and mixtures thereof) nitromethane, water and isopropanol orsecondary butanol form quaternary azeotropic mixtures which are usefulas dry cleaning solvents and are particularly useful for the removal ofhard-to-remove stains from leather.

BACKGROUND OF THE INVENTION In conventional dry cleaning processes forthe removal of dirt, grease and various soils from textile and leatherarticles, use is made of organic solvents having dissolved therein adetergent in minor amounts. The dry-cleaning bath may also contain otheradditives such as water, textile softeners, water repellents and thelike.

Solvents commonly used as the organic components of such dry cleaningcompositions include saturated aliphatic hydrocarbons such as Stoddardsolvent, gasoline or other low boiling paraffinic hydrocarbons;low-boiling aromatic hydrocarbons, such as benzene, toluene, and xylene;and low-boiling polyhalogenated hydrocarbons of l to 2 carbon atoms suchas carbon tetrachloride, methyl chloroform, trichloroethylene,tetrachloroethylene, trichlorofluoromethane, dichlorotrifluoroethane,trichlorodifluoroeth ane, and mixtures of these.

Numerous anionic, cationic, and nonionic detergents have been used asadditives to the dry cleaning compositions. Such additives, are known tohave adverse effects when contacted with leather articles in that theyremove the natural oil or grease from the leather leaving it harsh andbrittle.

Other candidate solvent compositions, although having satisfactorysolvency characteristics, are flammable and/ or toxic, thereby creatinghazards to personnel in their use. In addition, because of the diversecharacter of the many stains and solids encountered and the manydifferent types of textiles, both natural and synthetic, which areencountered by dry cleaning establishments, much dry cleaning mustpractically be carried out on a custom basis and requires hand spottingto remove deep stains.

The stains encountered in the dry cleaning process can be broadlycategorized as organic solvent-soluble and water-soluble. Thus, greaseand oil stains can be effectively removed by organic solvents such asperchloroethylene, while catsup, perspiration, common dirt stains andthe like are removed by water. Since both types of stains or soils areusually present on garments and the like submitted for dry cleaning, itwould be desirable to include both organic solvents and water in the drycleaning liquor. Since water and the common dry cleaning solvents arenot mutually soluble to any useful extent, it is general practice inthis art, as noted above, to utilize emulsifying agents, such asalkylaryl sulfonates, to increase the water tolerance of the organicsolvents. To obtain an effective increase in the water tolerance of manydry cleaning solvents requires the use of relatively large proportionsof emulsifying agent. This not only increases the cost of the solventmixture but also such large proportions of emulsifying agent adverselyaffect the material being cleaned,

for example, by removing natural oils, sizing agents, water proofingresins, and the like. Moreover, many textile materials are sensitive toexcessive moisture. Wool, for example, may shrink, and rayon and certainsynthetics may wrinkle when cleaned with solvents containing excessivemoisture. A delicate balance between organic solvents and water must bemaintained.

It is common practice to use polyhalogenated lower alkanes such astrichlorotrifluoroethane, tetrachlorodifluoroethane, and the like, forsolvent cleaning of a variety of materials. Such compounds are notablyof low toxicity for warm blooded animals and are non-flammable. However,such solvents are not entirely for use in dry cleaning of textilematerials since no known single compound is an effective solvent for thewide variety of stains encountered.

A variety of solvent mixtures have been tested for such purposes butgenerally have been found to be lacking to a greater or lesser extent inone or more of the desired characteristics of dry cleaning mixtures.Such mixtures may contain two or more halocarbons or at least onehalocarbon together with another organic compound such as an alcohol,ether, or ketone. In the usual instance, such mixtures are not constantboiling, that is they fraction-ate during use and during reclamation,losing one or more of the more volatile components. Such mixtures withaltered compositions may have less desirable properties such as lowersolvency for stains, less inertness towards textile materials andincreased flammability.

A number of azeotropic mixtures have been suggested for cleaning of avariety of materials. Azeotropes do not suffer from the above discussedfractionation disadvantage possessed by non-constant boiling mixtures.Unfortunately, the solvency character of the known azeotropiccompositions leave much to be desired when employed in the cry cleaningof most textile materials and, particularly, leather articles. Suchcompositions have very low tolerance for water and hence, whileeifective to remove oil-soluble stains, are efiective to removewater-soluble stains.

Moreover, although azeotropic compositions possess the above describedadvantages over non-azeotropic (non-constant boiling) compositions, asevidenced by the disclosure in US. Pat. 3,085,065 to Kvalnes, a basishas not been found for predicting the formation of azeotropes between oramong halocarbons, much less mixtures of halocarbons and other organiccompounds and/ or water.

It is, therefore, a major object of this invention to provide novelsolvent compositions for removing stains normally encountered on textilematerials and leather which novel solvent compositions exhibit a highdegree of solvency for such stains.

Another object of this invention is to provide novel solventcompositions which are constant boiling or essentially constant boiling.

Still another object is to provide novel solvent compositions containingan organic solvent and water which exhibit high solvency toward bothoil-soluble and watersoluble stains.

SUMMARY OF INVENTION In accordance with the present invention, we havediscovered constant boiling mixtures which are highly effective drycleaning solvents for removing common household stains, and which do notinclude a detergent compound. The novel constant boiling mixtures of ourinvention consist essentially of tetrachlorodifluoroethane,nitromethane, water and isopropanol or secondary butanol.

More particularly our invention includes the novel azeotropic mixturesconsisting essentially of about 76.8 weight percent oftetrachlorodifluoroethane, about 9.3 weight percent of nitromethane,about 3.7 weight percent of Water,

and about 10.2 weight percent of isopropanol. These quaternaryazeotropic mixtures of the invention boil at about 69.0 C. at 760 mm.pressure.

The invention also includes the novel azeotropic mixtures consistingessentially of about 78.6 weight percent of tetrachlorodifluoroethane,about 14.1 weight percent of nitromethane, about 4.7 weight percent ofwater, and about 2.6 weight percent of secondary butanol. Thesequaternary azeotropic mixtures of this invention boil at about 70.5 C.at 760 mm. pressure.

These novel solvent mixtures are constant boiling or essentiallyconstant boiling and thus can be recovered after use by distillationwithout change in composition or solvent properties.

The novel solvent mixtures have been found to be effective cleaningcompositions for leather and in use are contracted with the soiledleather for a period of time sufiicient to effect substantially completedissolution of the oil-soluble and water-soluble stains, such as catsup,can be removed without noticeably reducing the flexibility or softness(hand) of the leather article.

The novel quaternary solvent mixtures of the invention on standing,separate into two layers. However we have found that the separatedmixtures can be readily dispersed to uniform emulsions by gentleagitation and without recourse to emulsifying agents.

The lower layers which separate from the quaternary mixtures on standingare highly effective dry cleaning solvents for textile materials such aswool and in use are contacted with the soiled textile materials for aperiod of time sufiicient to effect substantially complete dissolutionof the oil-soluble and water-soluble stains. These lower layers containonly a minimum concentration of water and hence while effective for theremoval of water-soluble stains, do not cause shrinkage of wool orwrinkling of rayon.

The lower layer obtained from the isopropanol containing azeotropes hasthe approximate composition of Percent Tetrachlorodifluoroethane 80.00Isopropanol 9.7 Nitromethane 9.3 Water 1.0

This layer amounts to about 96% of the original quaternary azeotropicmixture.

The upper layer contains substantially none of thetetrachlorodifluoroethane. This layer contains about Percent Water 69.0

Isopropanol 22.2 Nitromethane 8.8

Percent Tetrachlorodifluoroethane 89.36 Sec.-butanol 2.0 Nitromethane 8.6

Water 0.04

This layer amounts to about 95% of the original quaternary azeotropicmixture.

The upper layer contains substantially none of thetetrachlorodifluoroethane. This layer contains about Percent Water 82.2Sec.-butanol 4.6 Nitromethane 13.2

This layer, which amounts to less than 5% of the azeotrope, may likewisebe drawn off and either discarded or admixed with additionaltetrachlorodifluoroethane and the mixture distilled to recover anadditional quantity of the quaternary azeotrope.

The halocarbon component of the novel quaternary mixtures of theinvention is available commercially as a mixture of about 69 mol percentof the symmetrical isomer, 1,1,2,2 tetrachloro-Z,2-difluoroethane andabout 31 mol percent of the asymmetrical isomer, l,1,l,2-tetrachloro-2,Z-difluoroethane. We have found that either isomer, per se, or thecommercially available mixtures thereof, when admixed with nitromethane,secondary butanol or isopropanol and water, yield azeotropic mixtures ofsubstantially identical characteristics and properties. Accordingly, allreferences contained in this specification to tetrachlorodifiuoroethaneapply to mixtures of the two isomers, in any proportions, or to eitherisomer, per se.

The following examples will illustrate the invention. Unless otherwiseindicated, parts and percentages are by weight and temperaturesare givenin degrees centigrade.

EXAMPLE 1 Preparation of the quaternary azeotrope PercentTetrachlorodifluoroethane 76.8 Isopropanol 10.2 Nitromethane 9.3 Water3.7

On standing, the fraction separated into two layers. The lower layer,which constituted 96.0% of the total fraction, was analyzed by gasliquid chromatography and was found to possess the following compositionPercent Tetrachlorodifluoroethane 80.0 Isopropanol 9.7 Nitromethane 9.3Water 1.0

(b) Repetition of the procedure set out in part (a), but substituting anequivalent amount of pure (97 mole percent)1,1,2,2-tetrach1oro-1,2-difluoroethane for the commercially availablemixture of isomers gave a quaternary azeotrope boiling at 69.1 and 760mm. pressure and having essentially the same composition as that mixtureobtained by using the commercial mixture of tetrachlorodifluoroethaneisomers.

(c) Repetition of the procedure set out in part (a), above, butsubstituting an equivalent amount of 1,1,l,2tetrachloro-2,2-difluoroethane for the commercial mixture of isomersgave a quaternary azeotrope boiling at 686 at 760 mm. pressure andhaving essentially the same composition.

These results indicate that azeotropic mixtures in accordance with ourinvention can be obtained using either pure isomers oftetrachlorodifluoroethane or any mixture thereof. Such azeotropespossess substantially iden tical compositions and have no significantdifference in properties.

EXAMPLE 2 Preparation of quaternary azeotrope (a) Equimolecularquantities of tetrachlorodifluoroethane (B.P. 92.8"), the commerciallyavailable mixture,

Percent Tetrachlorodifluoroethane 78.6 Sec.-butano1 2.6 Nitromethane14.1 Water 4.7

On standing, the fraction separated into two layers. The lower layer,which constituted 95.3% of the total fraction, was analyzed by gasliquid chromatography and was found to possess the followingcomposition:

Percent Tetrachlorodifluoroethane 89.36 Sec.-butanol 2.0 Nitromethane8.6 Water 0.04

(b) Repetition of the procedure set out in part (a), but substituting anequivalent amount of pure (97 mole percent),1,1,2,2-tetrachloro-1,2-difiuoroethane for the commercially availablemixture of isomers gave a quaternary azeotrope boiling at 70.3" at 760mm. pressure and having essentially the same composition as that mixtureobtained by using the commercial mixture of tetrachlorodifiuoroethaneisomers.

(c) Repetition of the procedure set out in part (a), above, butsubstituting an equivalent amount of 1,l,1,2-tetrachloro-2,2-difiuoroethane for the commercial mixture of isomersgave a quaternary azeotrope boiling at 70.7 at 760 mm. pressure andhaving essentially the same composition.

These results indicate that azetropic mixtures in accordance with ourinvention can be obtained using either pure isomers oftetrachlorodifluoroethane or any mixture thereof. Such azeotropespossess substantially identical compositions and have no significantdifference in properties.

EXAMPLE 3 Use of the quaternary azeotrope as a dry cleaning solvent forleather Swatches of natural (undyed) sheepskin suede leather, 2 in. x 8in., were soiled with one of the following: lip stick, catsup, grapejuice or lanolin. The stains were allowed to dry and to set for 24 hoursat ambient temperature. The stained swatches were then cleaned in anagitated bath containing about 350 cc. of a particular test cleaningsolvent.

The cleaning cycle was carried out for /2 hour and at ambienttemperature.

The test solvents used were the azeotrope prepared in Example 1, part(a) above, the respective components of the azeotrope, andperchloroethylene, a well known, commercially available dry cleaningsolvent.

The results of these tests are set out in tabular form in Table 1 below.The effectiveness of the stain removal was rated by visual observationon a scale of 1 to with 1 being substantially no stain removal and 10being complete removal of the stain.

These results indicate the general overall effectiveness of theazeotrope composition as a soil remover from suede leather. Othersolvents tested, while as good for removal of a particular soil, areineffective with respect to removal of one or more of the other stainstested.

The data set out in Table 1 indicate the presence of synergism in thequaternary mixture of the invention. The numerical ratings areapproximations of the percentage removal of the several stains, that isa rating of 5 is equivalent to about 50% removal of the stain. Thesepercentages multiplied by the concentration of the particular solvent inthe quaternary mixture give a quantitative indication of the amount ofthe stain which would be expected to be removed by the solvent in themixture. The sum of these results in each instance is less than theanalogous value (ratingXlO) actually obtained with the quaternarymixture.

Thus a quantitative summation of the removal of lipstick stain by eachof the four component solvents totals 61.5% whereas the quaternarymixture removed 100% of the stain.

The total grape juice removed would be expected to be 60.57%. Actually100% of this stain was removed by the azeotrope.

The total catsup removed would be expected to be 39.74%. Actually, 100%of the stain was removed.

The total lanolin removed would be expected to be 96.7%. Actually 100%of the lanolin was removed by the quaternary azeotrope.

Accordingly, based on this method of calculation, the novel quaternaryazeotrope of the invention exhibits a synergistic effect in the removalof both oil-soluble and water-soluble stains from leather.

EXAMPLE 4 Use of the quaternary azeotrope containing sec.butanol as adry cleaning solvent for leather In an analogous manner to thatdescribed in Example 3 above, the quaternary azeotrope containingsecondary butanol prepared in Example 2, part (a) above, was tested as adry cleaning solvent for soiled suede leather. In this instance Stoddardsolvent, a well-known commercially available dry cleaning solvent, wasused in place of perchloroethylene as a standard.

The results of these tests are set out in Table II below.

These results indicate the general overall eifectiveness of theazeotrope composition as a soil remover from suede leather. Othersolvents tested, while as good or slightly superior from removal of aparticular soil, are inelfective with respect to removal of one or moreof the other stains tested. Using the method of calculation described inExample 3 above the data of Table II can likewise be used to indicatethe presence of synergism in the azeotropic mixture tested in thisexample.

Thus a quantitative summation of the removal of lipstick stain by eachof the four component solvents totals 56.4% whereas the quaternarymixture removed 100% of the stain.

The total grape juice removed would be expected to be 51.4%. Actually,of this stain was removed by the azeotrope.

The total catsup removed would be expected to be 35.34%. Actually, 90%of the stain was removed.

The total lanolin removed would be expected to be 93.2%. Actually of thelanolin was removed by the quaternary azeotrope.

Accordingly, based on this method of calculation, the novel quaternaryazeotrope of the invention exhibits a synergistic effect in the removalof both oil-soluble and water-soluble stains from leather.

EXAMPLE Dry cleaning of water sensitive textiles with lower layer ofazeotrope Certain te'xtile materials, such as wool are sensitive toexcessive moisture in dry cleaning solvents. Such sensitivity isevidenced by shrinkage. Some moisture is desirable, however, foretfective cleaning.

As has been indicated, the quaternary azeotropes on standing, separateinto two phases, the lower of which contains only a minimum quantity ofwater. This amount, in the presence of the organic solvents does notcause shrinkage and/or wrinkling of textiles during the cleaning of saidtextiles. The avoidance of shrinkage serves to preserve the originalcharacter of the cleaned textile. The absence of wrinkles reduces oreliminates the need for pressing of the cleaned textile.

This property of the lower phase of the azeotrope is shown by thefollowing comparative test wherein the etfect of this mixture ofsolvents on wool and rayon textile material was compared with a standarddry cleaning composition. The standard consisted of perchloroethylenecontaining 1% of water and 1% of Aerosol 0T (a synthetic detergentconsisting essentially of the sodium salt of dioctylsulfosuccinic acid).

In this test, measured swatches of the particular textile material wereimmersed in an agitated bath of the dry cleaning solvent composition for/2 hour at ambient temperature. After removal from the bath. theswatches were dried and remeasured for shrinkage. The samples, aftercleaning, were checked for the presence of wrinkles.

The results of these tests are recorded in Table HI below:

1 Average shrinkage of 2 Perchloroethylene containing 1% water and 1%Aerosol OT.

The used lower layer solvent mixture can be readily recovered by passingthe solvent through a filter to remove solid particles. To the filtratea mixture of about 4% water, 0.3% sec.-butanol and 0.8% nitromethane ora mixture of about 4% water, 0.88% isopropanol and 0.35% nitromethane isadded and the mass is fed to a still. On distillation, a quaternaryazeotrope of the same composition as that obtained in Example 2, part(a) above or Example 1, part (a), above is obtained. This is permittedto stratify and the lower layer is drawn oil to a suitable storagevessel to be recycled. The upper layer of the azeotrope can be preservedfor use as build up for used solvent in this recovery process. The stillbottoms, consisting essentially of water and dissolved soil, arediscarded.

The novel solvent mixtures of the invention find other solventapplicants such as for removing gases, oils and inorganic salts from avariety of industrial items, for

cleaning of photographic films and prints, for removal of bufiingcompounds, such as rouge, and also may be used as heat exchange mediaand as chemical reaction media.

'It will be apparent to those skilled in the art that, for specializedpurposes, various additives could be ire corporated with the novelmixtures of the invention, for example lubricants, water proofingresins, moth proofing chemicals and the like. These additives are chosenand used in amounts so as not to adversely alfect the essentialproperties of the mixtures for a given purpose.

The invention is not intended to be limited by any specific embodimentsdisclosed herein, but only by the scope of the following claims.

We claim:

1. Constant boiling mixtures consisting essentially of about 76.8 weightpercent of tetrachlorodifiuoroethane, about 10.2 weight percent ofisopropanol, about 9.3 weight percent of nitromethane and about 3.7weight percent of water, said mixtures boiling at about 70.5 C. at 760mm.

2. Constant boiling mixtures as described in claim 1 in which thetetrachlorodifiuoroethane is a mixture of about 69 mol percent of1,1,2,2-tetrachloro-1,2-difiuoroethane and about 31 mol percent of1,1,1,2-tetrachloro- 2,2-difiuoroethane.

3. Constant boiling mixtures as described in claim 1 in which thetetrachlorodifiuoroethane is substantially pure1,1,2,2-tetrachloro-1,2-difiuoroethane.

4. Constant boiling mixtures as described in claim 1 in which thetetrachlorodifiuoroethane is substantially pure 1,1,1,2-tetrachloro-2,2-difluoroethane.

5. Constant boiling mixtures consisting essentially of about 78.6 weightpercent of tetrachlorodifiuoroethane, about 2.6 weight percent ofsecondary butanol, about 14.1 weight percent of nitromethane and about4.7 weight percent of Water, said mixtures boiling at about 70.5 C. at760 mm.

6. Constant boiling mixtures as described in claim 5 in which thetetrachlorodifiuoroethane is a mixture of about 69 mol percent of1,-1,2,2-tetrachloro-1,2-difluoroethane and about 31 mol percent of1,1,1,2-tetrachloro-2,2-difluoroethane.

7. Constant boiling mixtures as described in claim 5 in which thetetrachlorodifiuoroethane is substantially pure1,1,2,2-tetrachloro-1,2-difiuoroethane.

8. Constant boiling mixtures as described in claim 5 in which thetetrachlorodifiuoroethane is substantially pure 1,1,1,2-tetrachloro-2,Z-difluoroethane.

9. The process of dry cleaning leather which comprises contacting for aperiod of time sufficient to efiect substantially complete dissolutionof oil-soluble and Watersoluble stains, leather to be cleaned with aconstant boiling mixture as described in claim 1, separating saidleather from said constant boiling mixture and drying said leather.

10. The process of dry cleaning leather which comprises contacting for aperiod of time sufiicient to effect substantially complete dissolutionof oil-soluble and water-soluble stains, leather to be cleaned with aconstant boiling mixture as described in claim 5, separating saidleather from said constant boiling mixture and drying said leather.

References Cited UNITED STATES PATENTS 3,285,858 11/1966 Hirsch et a1252l71 3,085,116 4/ 1963 K valnes 260'652.'5 3,530,073 9/1970 Clark etal 252DIG. 9 3,042,479 7/ 1962 Hicks et a1. 8-142 L'EON D. ROSDOL,Primary Examiner W. E. SCHULZ, Assistant Examiner U.S. Cl. X.R.

8--142; 252DIG. 9; 260652.5

